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Forest Service
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Research Paper PNW-165
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ill Pacific Northwest
U.
and Range
of
Iture
Station
orest Service
Portland,
Seven-year response of 35-year-old Douglas-fir to nitrogen fertilizer.
Page
INTRODUCTION . . . . . . . . .
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RESULTS AND DISCUSSION .
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Tree Damage and Mortality
Winter Breakage Was the Major Cause of Damage and Mortality
D. b. h. Growth
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Average D. b. h. Growth Was Increased by Fertilizing
D. b. h. Growth of Larger Trees Particularly
Stimulated by Nitrogen
Height Growth
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Increasing Fertilizer Dosages Increased Response
Continued Stimulation of Height Growth Is Likely .
Cubic- Volume Growth
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Gross Volume Growth per Acre Was Markedly Improved
Continued Response Is Predictable From Trends
of Annual Volume Growth
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Mortality Volume Was Increased by Heavy Dosages of N
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Net Cubic- Volume Growth Was Grcatest With 280 Pounds N
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CONSIDERATIONS FOR THE LAND MANAGER
What Rates of Nitrogen Should Be Used?
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What Source of Nitrogcn Should Be Used?
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Fcrtilizer Can Increase Usable Yields
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Combination of Fertilizing anel Thinning Holds
Pa rticular Promisc
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Effect of Nitrogen Fertilization on Water Quality.
LITERATURE CITED
APPENDIX
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Pretreatment Conditions
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Experimental Design and Treatment .
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l\Ieasurements anel Volume Determination .
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Applying ammonium nitrate fertilizer to a Site V plantation resulted in Significant increases
in tree diameter, height growth, and in volume growth during thc 7 years following treatment.
Dosages of 140, 280, and 420 pounds of nitrogen per acre incrcased gross volume growth by 55,
H2, and 10H percent,respectively (515, 852, and 1,012 cubic feet per acre); the increase with the
140 N dosage was equivalent to a temporary improvement of site quality by one site class (30 fect
on a lOO-year basis).
Continued response in total and merchantable volume is likely, especially
with higher dosages of nitrogen.
The 280- and 420-pound-N dosages increased winter breakage,
primarily in smaller trees, and at least doubled the number of trees and cubic volume lost to mor­
tality.
Thus far, net gain in total cubic volume of the live stmld from fertilizing is as much as 83
percent (64H cubic feet), with maximum gain from the 280-pound-N treatment.
Nitrogen fertilizer
is a promiSing silvicultural tool for increaSing wood production of Douglas-fir stands on similar
soils of low natural productivity.
Keywords:
Diameter increment, Douglas-fir, fertilizer response
(forest tree), height
increment, nitrogen fertilizer response, Pseudotsuga menz,:esii, silviculture,
site productivity, volume increment, winter damage (forest).
R. E. Miller is Principal Soil Scientist at Forestry Sciences Laboratory,
Pacific Northwest Forest and Range Expcriment Station, Olympia, Washington.
L. V. Pienaar is Associate Professor of Forest Biometrics, School of
Forestry, University of Georgia, Athens, Georgia.
INTRODUCTION During the past 20 years, various fertilizers have been tested in Douglas-fir
forests of western Washington and Oregon. In most tests, nitrogen has increased
tree growth (Strand and Miller 1969). Some land managers have quickly adopted
nitrogen fertilizing as a silvicultural tool for increasing production; other managers
lack organizational or financial flexibility to implement a fertilizing program or
lack sufficiently strong evidence of expected volume or value gains from their own
lands.
Reliable data on volume response and its distribution by tree sizes are basic
in any decision to implement or continue a forest fertilizing program. The major
purpose of this paper is to provide such response data from a specific study area in
a 37-year-old, Site V, Douglas-fir plantation on the Wind River Experimental Forest
in southwestern Washington. In the initial report, Reukema (1968) reported sub­
stantial increases in height, diameter, and basal area growth per acre during the
first 4 years after fertilizing. This present report describes the continuing effects
I
of fertilizer on diameter and height of individual trees and cubic volume' growth per
acre.
In April 1964, ammonium nitrate (33. 5 percent N) was applied to this plantation
(fig. 1) at rates of 140, 280, and 420 pounds per acre. Trees were measured prior
to treatment, after two growing seasons, and then annually through 1970. Additional
details about the experimental stand, design, treatment, and data analysis are pro­
vided in the appendix.
Figure l.--An unfertilized plot in the study area.
RESULTS AND DISCUSSION TREE DAMAGE AND MORTALITY
During the 7 years after treatment, 12 to 37 percent of the initial trees died;
more than twice as many trees died on plots treated with 280 and 420 pounds of nitrogen
per acre as on untreated plots (table 1). Mortality waS largely confined to smaller
trees; only 5 percent were in the upper third of the diameter range, whereas 60 per­
cent were in the lower third.
Winter Breakage Was the Major Cause of Damage and Mortality
Most mortality was caused by or associated with winter breakage, presumably
the mixed effects of snow, ice, and wind. Serious winter damage to forests in the
general study area occurs every 2 to 3 years.Y Winter breakage caused 78 to 79
percent of the total mortality on control and 140 N plots and 87 and 88 percent, res­
pectively, on plots treated with 280 and 420 pounds of nitrogen per acre.
fIigher
dosages of nitrogen led to increased mortality, because more trees were d'amaged
and a higher percentage of damaged trees subsequently died (table 1). Mortality in
given years was clustered, rather than randomly distributed, within the plot; this
suggests that excessive winter breakage probably caused temporary loss of site
occupancy and volume growth.
1/
Personal correspondence with David Jay, who was District Ranger, Gifford Pinchot National Forest, in February 1972. Table 1 .--Tree mortality after seven growing seasons by treatment and cause,
per acre basis, average of three plots per treatment
Trea tment.ll
Live,
T963
1963-70
-------NUmbep------0
Total
I
Pepoent ------NUmbep------
93
16
113
Breakage mortalit
Tota1 morta1i ty
Died
73
Pep oentY
65
Pi3Poent
78
140
573
67
12
107
53
50
79
280
627
193
31
220
167
76
87
420
620
227
37
260
200
77
88
.lI
Y
2
600
Winter breakage
Total dead,
Pounds of nitrogen per acre.
Percent of damaged trees;
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Why should nitrogen application to this stand lead to greater tree breakage and
mortality, especially in smaller trees? The most plausible explanation is that the
near doubling of needle length observed during the first growing season after ferti­
lizing.e./ resulted in greater accumulation of snow and ice and greater resistance to
wind. The comparable height growth response of smaller trees to nitrogen suggests
that their needle and twig length were also increased as much as those of larger
trees. Although smaller trees are commonly sheltered by larger trees and pre­
sumably less subject to direct climate effects, these smaller trees can be targets
for clumps of accumulated snow falling from larger trees. Similar increases in
snow breakage after needle quantity was increased by greatly improved nitrogen nutri­
tion on lower quality sites have been reported for Scots pine (Kreutzer 1967) and for
Norway spruce (Nebe 1970).
It is unlikely that reduced wood strength could have been a major contributing
factor to increased winter breakage, despite increases in ring width which occurred
during the second growing season after treatment. Severe breakage occurred through
out the study area in the winter preceding fertilizing. During the s cond winter after
treatment, however, numbers of trees damaged differed significantiy among treat­
ments and increased as fertilizer rates increased (Reukema 1968). It seems unlikely
that the proportion of possibly weaker wood produced in the two growing seasons after
fertilizing would sufficiently weaken the entire bole which was generally several
inches in diameter at the breaking point.
D.B.H. GROWTH
We examined the effect of ammonium nitrate on (1) change in average d. b. h.
(of plots), (2) average diameter growth of surviving trees, and (3) diameter growth
by d. b. h. classes. The rate of diameter growth during the 7-year period increased
progressively with increased dosages of fertilizer; continued response is indicated.
Average D.b.h. Growth Was Increased by Fertilizing
After seven growing seasons, increases in average d. b. h. of plots and d. b. h.
growth of surviving trees were closely related to the amount of nitrogen applied
(table ). When compared with growth on untreated plots, average diameter growth
was m re than: doubled by the 280-N and 420-N treatments.
In both fertilized and unfertilized stands, part of the increase in average d. b. h.
was due to mortality. In addition to providing more growing space to surviving trees,
mortality caused an immediate increase in average d. b. h. that was not a result of
growth, but rather the result of losses of smaller-than-average trees.
Average diameter growth of surviving trees was linearly related to amounts of
nitrogen applied (fig. 2). Although the response per pound of applied nitrogen appeared
to lessen at the 420-pound dosage, there was no significant curvilinear component to
?:! Personal
correspondence with Robert Tarrant, Research Forester, Pacific N orthwest Forest and Range Experiment Station, in March 1972. 3
Table 2.--Changes in live trees per acre and average d.b.h.
Live trees
TreatmentlJ
1963
I
1970
-----NUmber-----
Average
d.b.h.,
1963
Increase in
average d.b.h.
D.b.h. growth o
surviving trees
Inch es ---------------------
------------------------
0
600
507
5.4
1.0
140
573
507
5.3
1.3
1.1
2 0
627
433
5.4
2.2
1.5
420
620
393
2.3
1.8
5.3
0.7
lJ Pounds of nitrogen per acre.
Average d.b.h. of live trees in 1970 minus average d.b.h. of live trees in
1963; weighted average of three plots per treatment.
Average d.b.h. growth of trees surviving in 1970, weighted average of
three plots per treatment.
2.0
•
1.8
1.6
Vi
w
J:
U
1.4
;!!;
J:
'\'\
0'
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o
o'l-
1.2
0
a:
(!)
:i
CD
ci
•
1.0
"I
• =
Plot
mean
0.8
0.6
O
______
______
140
o
______
______
_L______
______
280
420
NITROGEN APPLIED (POUNDS PER ACRE)
Figure
2.--Average
7-year-d.b.h. growth after fertilizing.
(Weighted average of three plots per treatment.)
4
the response surface (p < 0. 11). Thus the 420-pound-N treatment was not large enough
to determine the dosage of N at which d. b. h. growth would have leveled off.
D.b.h. Growth of Larger Trees Particularly Stimulated by Nitrogen
In all plots, diameter growth of surviving trees was significantly related to
initial tree size; largest trees grew most in d. b.h. Fertilizing enhanced this relation­
ship. Additions of 280 and 420 pounds of nitrogen per acre significantly increased
growth of larger trees more than that of smaller trees (fig. 3). The 140-N dosag'e
also differentially increased the growth of larger trees but to a lesser extent than
higher dosages. Because higher fertilizer dosages resulted in greater mortality,
the increase in d. b. h. growth of larger trees following the 280- and 420-N treatments
is explained in part by release as well as by improved nutrient status. The antici­
pated effects of this fertilization on future stand structure are increased average
diameter and d. b. h. range, also continued advantage of large trees over small trees.
5
4
420 N
Iii
w
J:
u
Z
3
J: ,'1
0
a:
(!l
140 N
2
::t: a:i
ci
......
o
2
______
______
______
____
o
4
6
.......
..... 0 N
______
8
______
10
12
INITIAL D.B.H. (INCHES)
Figure 3.--Average 7-year-d.b.h. growth of trees of varying
initial d.b.h. and treatment.
5
HEIGHT GROWTH
We examined fertilizer effects on total and periodic annual height growth during
the 7-year period after treatment. Height growth was accelerated by fertilizer; con­
tinued response is indicated, particularly by trees treated with 280 and 420 pounds of
N per acre.
Increasing Fertilizer Dosages Increased Response
We compared average height growth of 31 to 34 trees per dosage level; height of
these trees had been measured at the start and end of the 7-year period. Approximately
two-thirds of these sample trees were randomly drawn from trees with d.b.h. exceed­
ing and one-third from trees less than the average of their respective plot. On 10 of the
12 plots, 7-year height growth was not significantly correlated with initial height; only
one control plot and one plot treated with 140 pounds N were exceptions. Thus although
average initial height of sample trees was somewhat greater on plots with the two highest
dosages of N, it is unlikely that any serious bias was introduced.
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Average 7-year,height growth in fertilized plots was 34 to 89 percent greater
than in unfertilized (table 3). Although there is some evidence that growth increases
gradually diminished with higher levels of fertilizer (table 3), this tendency for
curvilinearity was statistically nonsignificant (p < O.20); analysis of variance supported
a linear response surface (p < O.001) for the range of dosages tested (fig. 4).
Continued Stimulation of Height Growth Is Likely
We examined the trends of mean annual height growth on 14 to 17 trees per
treatment level. These trees, measured at each inventory, were of varying initial
heights.
Annual height growth showed cyclic trends with no apparent relation to growing
Season precipitation (fig. 5). In general, fertilized and control trees had similar
growth trends; however, growth of fertilized trees exceeded that of control trees in all
years. Thus far, the yearly trend of height growth on plots treated with 280 pounds
of nitrogen per acre is about the same as on those treated with 420 pounds. Height
growth response following the 140-N treatment was consistently less than that follow­
ing heavier ,dosages, yet was still evident in the seventh growing season. Continued
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response i s likely, particularly by trees treated with 280 and 420 N.
CUBIC-VOLUME GROWTH
In this section, we examine the effects of fertilizing on:
1. Growth in total stem volume (including top and stump) of all trees 1.5 inches
and larger (CVTS); this is our best estimate of total stand production.
2. Change in cubic volume to a 4.O-inch-top d.i.b. (but excluding a 1.5-foot
stump) of all trees 5. 6-inch d.b.h. and larger (CV4); this estimates merchantable
volume production assuming intensive utilization standards.
3. Trend of annual volume growth to determine when response to fertilizer
started, peaked, and ended.
4. Gross versus net growth.
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Table 3.--Averag
TreatmentY
and plo e/
el!
7-year height growth by treatment and plot
Average
initial
height
Average
growth
Gain from treatment
Feet----------------
-----------------
Percent
0:
7
1
5
All plots
42.8
40.3
44.5
8.8
6.6
8.7
42.5
8.0
40.6
39.6
44.0
11.7
10.3
10.5
41. 7
10.7
47.6
39.8
48.1
13.6
14.0
14.7
45.0
14.1
45.0
42.7
45.6
16.1
15.6 13.5 44.3
15.1
140:
3
9
8
All plots
2.7
34
6.1
76
7.1
89
280:.
2
12
11
All plots
420:
6
4
10
All plots
11
y
'Y
Treatment averages are based on 31-34 trees.
Pounds of nitrogen per acre.
Plots are arranged within treatment in ascending order of
initial total cubic volume.
7
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16
15
14
13
w
:z:: u
z
:z::
0
a:: <!l t:z::
<!l iii :z:: 12
11 • =
Plot
mean
10
9
8
.,)
7
,
..
6
140
280
NITROGEN APPLIED (POUNDS PER ACRE)
Figure 4.--Average 7-year height growth after fertilizing.
(Weighted average of three plots per treatment.)
8
420
II
(!)
W
3.0
I
...J
<
::::>t:u
Zw
Zu.
<I
w
(!)<0
280 N
2.0
""'
.,
/\"
,"'"
. /
1
"
•
1.0
0 0
.
'420 N
/,140 N
..... ....
.
. 0 N
."
:
ffia:
>(!)
<
'I
1
/
:l
ill
2
3
4
5
6
7
(f)
w
I
u
40 Z
20 Z
0
«
a:
YEARS AFTER TREATMENT
Figure 5.--Average yearly height growth by
treatment and year since treatment re­
lated to estimated rainfall during
growing season.
The method used to determine tree and plot volumes is detailed in the appendix.
Although there were initial differences in both total (CVTS) and merchantable (CV4)
volume among plots and treatment levels, subsequent volume growth in CVTS, but
not CV4, was significantly correlated with volume of the initial growing stock
(p < O. 002). Therefore, CVTS growth was adjusted by covariance to common initial
volumes and adjusted growth used to determine fertilizer gain and trends of annual
volume growth.
Gross Volume Growth per Acre Was Markedly Improved
TotaZ voZwne growth. -- During the 7 years following treatment, total cubic­
volume growth of all trees, 1.5-inch d.b.h. and larger, was positively related to
amount of, nitrogen applied (table 4); the response surface was significantly curvi­
linear (p < 0.06) (fig. 6). Depending on fertilizer rate, gross growth on fertilized
plots averaged 55 to 109 percent greater than that on control plots. Corresponding gains
in volume growth averaged 515 to 1, 012 cubic feet and increased with nitrogen dosage.
The average increase follOWing the 140-N dosage was equivalent to a temporary
improvement of site quality by one site class (30 feet on a 100-year basis).
The response surface was better described by a curved than a straight line.
For example, the adjusted treatment means before smoothing clearly showed that
volumes gained from the three dosages gradually declined from 3.4 through 3.0 to
2.3 cubic feet per pound of nitrogen applied. Thus far, the optimum dosage of
ammonium nitrate for gross volume production on this area is near 140 pounds of
nitrogen per acre. To define the present or future response surface precisely will
require another experiment using narrower intervals of dosage and, if pOSSible,
more replications per dosage.
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Table 4.--Gross volume growth by treatment, 7-year period, per acre basis
and p10tY
0:
Volume growth
Initial stand
TreatmentlJ
cvTsli
CV411
cvTsli
Unadjusted
---------------------------------
7
1
5
1,617
1,842
2,282
781
954
1,087
772
859
1,125
Mean
1,914
941
919
3
9
8
1,446
1,878
2,214
650
811
1,215
1,163
1,249
1,652
Mean
1,846
892
1,355
2
12
11
1,,793
1,904
2,470
839
608
1,560
1,583
1,944
2,133
Mean
2,056
1,002
1,887
6
4
10
1,767
1,807
2,267
964
668
1,002
1,648
1,841
2,329
Mean
1,947
878
1,939
140:
280:
420:
I
CV411
Adjusted
Cubio
Unadjusted§!
I Adjusted
feet----------------------------------
685
931
1,296
930
971
1,023
1,180
1,331
1,668
1,445
1,393
1,412
1,694
2,126
2,172
1,782
1,997
1,801
1,685
2,042
2,471
1,942
2,066
2,190
lJ Rounds of nitrogen per acre. Y Cubic volume of total stem of all trees 1.5-inch d.b.h. and larger. 11 Plots are arranged within treatment in ascending order of initial total cubic volume. 11 Cubic volume to a 4.0-inch top d.i.b. of trees 5.6-inch d.b.h. and larger. Adjusted to a common initial plot volume for all treatments and smoothly curved
over N dosage.
§! Neither the covariate nor quadratic response surface proyed significant; p
and 0.27, respectively; smoothed by linear regression.
<
0.27
The volume increases after fertilizing this plantation exceed those predicted
for comparable nitrogen dosages applied in Similarly aged but natural stands on
site class 82 (Site V) land in the Puget Sound lowlands (Gessel et al. 1969).
Gessel et al. (1969)
Treatment
Growth
This study
Gain
(Cubic feet)
o
140
280
420
10
1,062
1,359
1,555
1,666
297
493
604
Growth
Gain
(Cubic feet)
930
1,445
1,782
1,942
515
852
1,012
1
2.400
Gross growth (adjusted) =
'
930.0 + 4.31 N-0.0045N
i=' 2,000
UJ
UJ
u..
U
co
:::>
u
UJ
a:
U
«
1,600
IlliJ Gross
D Net
Unadjusted means
• Net
o Gross
a:
UJ
a.
:I:
Net growt h (adjusted) =
'
784.1 + 4.22 N-0.0068N
1,200
o
a:
(!l
:::>
...J o
>
...J «
'Io
I-
800
400
NITROGEN APPLIED (POUNDS PER ACRE)
I
Figure 6.--Total gross and net volume growth
for a
7-year period by plot and treatment.
Although predicted growth for their untreated stands (1, 06::! cubic feet) is unexplain­
ably so much more than the 735 cubic feet predicted for normal, natural stands
(Staebler 1955), this possible overestimate of growth should also apply to their
growth estimates for treated stands. Average gains predicted by them for compar­
able ratEi)s of nitrogen and a comparable 7-year period are about 60 percent of those
attained in this study.
Change in gross merchantabZe voZwne. - Increase in CV4 (cubic volume to a
4.O-inch top d. i.b. of trees 5. 6-inch d. b. h. and larger) was also accelerated by
nitrogen (table 4). An additional 389 to 1, 167 cubic feet of merchantable wood was
produced in fertilized stands, relative to unfertilized stands, during the 7-year period:
-
Average gain in gross CV4 increment
Treatment
Cubic feet
Percent
140 N
280 N
420 N
389
778
1, 167
38
76
114
11
The accumulation of merchantable volume accelerated from increased growth
after treatment, as well as reclassification of nonmerchantable volume that existed
before treatment. Potentially, treatment can accelerate merchantable volume accu­
mulation when any of the following occurs. (1) More growth is added to portions of
merchantable stems. (2) Diameter growth of nonmerchantable trees is increased,
so they more quickly reach merchantable size (5. 6-inch d. b. h. in this study); upon
attaining this merchantable d. b. h . , the total merchantable stem volume (about 2.7
cubic feet), not just growth since treatment, is classified as "growth. " (3) Height
growth is increased so a longer merchantable stem results; part of the gain in mer­
chantable volume from increased length of merchantable stem is from reclassifica­
tion of previous nonmerchantable wood. In this study, more merchantable volume
undoubtedly resulted from accelerated height and diameter growth. It is doubtful,
however, that fertilization accelerated movement into merchantable d. b. h. classes.
Although more ingrowth into merchantable classes occurred on fertilized stands
following the 280- and 420-N treatments, there were initially more such trees
potentially available as ingrowth (table 5).
Table 5.--Number and proportion of larger than specified d.b.h. class trees
at ages 37 and 44. by treatment1l
TreatmentY
Merchantable ingrowth
duri ng 7 years
Initial live stand
2-inch +
d.b.h.
I
6-inch +
Potential
d.b.h.
I
Actual
I
Died
I
Final live standY
Live
2-inch +
d.b.h.
I
6-inch +
d.b.h.
----------------------------Numberof trees per dare-----------------------------o
140
280
420
273
273
213
233
600
573
627
620
327
300
413
387
107
107
160
'160
7
7
13
40
100
100
147
120
507
507
433
393
373
367
353
333
-------------------.--------Peraent of total number------------------------------46
48
34
38
o
140
280
420
11 Merchantable trees
d.b.h. and larger.
=
.1133
36
39
41
'if 6
74
72
82
85
6
8
25
trees 5.6-inch d.b.h. and larger; total trees
=
trees 1.5-inch
Y Pounds of nitrogen per acre.
died.
Totals may not agree because some of the original 6-inch+ d.b.h. trees subsequently
.11 Percent of potential ingrowth. 'if Percent of actual ingrowth. 12
Continued Response Is Predictable From Trends of Annual Volume Growth
Mean annual growth in cvrs of fertilized stands exceeded that of unfertilized
stands during each measurement period after fertilizing (fig. 7).
When did response stari;?--A statistically significant response to all nitrogen
dosages occurred during the 2-year period following fertilization. Although the trees
were not remeasured after the first growing season, increment cores showed a
definite response in radial growth during the first year after treatment.
Why fluctuations in annual growth?-- Yearly volume growth on both treated
and untreated stands progressed in a harmonic, up-down trend (fig. 7); years of
minimum and maximum growth on fertilized plots corresponded to those of the con­
trol. Gessel et al. (1D69) reported similar patterns of annual basal area growth in 40­
year-old, Site IV Douglas-fir near Shelton, Washington. They regarded these as
normal cyclic trends and also noted that growth of fertilized and unfe tilized stands
i
fluctuated similarly.
It seemed likely that fluctuations in cubic-volume growth in a given year should
be related to growing season precipitation of that year. However, a comparison of
yearly trends of growth on control plots and rainfall during April through October as
measured at the nearest weather station failed to reveal a simple relationship (fig. 7).
Unfortunately, we have insufficient information to evaluate precisely other explana­
tions.
When did response peak?--Volume responses apparently peaked 2 years
earlier with 140 pounds N per acre than those with heavier applications (fig. 7).
With 140 N, peak annual growth occurred in the third year and peak g<!in (over the
control), in the fourth year. With 280 and 420 pounds N per acre, peak annual
growth was in the fifth growing season, and gain was as great or greater in the sixth
year as in the fourth. Thus, with higher dosages, growth continued at near-peak
levels for several years; in contrast, growth with the 140-N treatment declined
rapidly after culmination.
Pe iuc response after heavy dosage of N in this study area was more prolonged
than that in a 40-year-old stand on gravelly soil of the Puget Sound lowlands (Gessel
et al. 1969). FollOWing application of 300 pounds N per acre, volume response
culminated in years 4 and 5 and declined rapidly thereafter. There was practically
no further response in years 7 and 8.
What is the duration of response?-- The duration, as well as magnitude,
of response to nitrogen fertilizer in this stand will probably depend on the nitrogen
dosage (fig. 7). Seven years after treatment, the response is still evident; the gain
in the seventh growing season was 19, 82, and 99 percent with 140, 280, and 420
pounds of nitrogen per acre, respectively. Although the effects of fertilizing with
140 N are likely to end within 10 years after treatment, those with heavier applica­
tions are likely to continue several years longer.
13
400
W
a:
u
<
a:
W
Il..
300
:x:
280 N
o
a:
Cl
W
:::E
/ij
:::>
...J W
OLL.
200
----1
-- 40 N
ON
>u
...Jm
< :::>
:::>
u
z-
100
\1
il
.',
z
<
o
iI
I
30
::;1
:',1:..:'1
6
7
.:: ,:
'----I._-'...._....I-__--'''--__..A.___.L-__....'--...:I
__.A----I
2
3
4
Iii
40
5
I:g
0
oc
YEARS AFTER TREATMENT
W
:::E
:::> ....
...J z
OW
>, u
a:
uw
-Il..
co_
:::>:x:
200
150
100
50
O
z
_a:
<Cl
Cl
140 N
0
1964
1965
1966
1967
1968
,.}
1969
1970
YEARS AFTER TREATMENT
Figure 7.--Trends of gross total volume growth and estimated rainfall
during the growing season:
Top, Growth adjusted for difference s
in initial volume, total stand in axis;
14
bottom, percent gain.
l
Response to nitrogen at this study area may last longer than that in Douglas-fir
stands on gravelly soils of the Puget Sound lowlands, where durations exceeding 12
years following a single application of nitrogen fertilizer have been measured (Handley
and Pienaar 1972) .w Heilman (1971) also found that duration of response depended
on the amount of fertilizer applied. For nine areas in southwest Washington, he
estimated that duration of response to a single application averaged 5 years with 200 N
and 7 years with 400 N.
•
Swnmary. - Ammonium nitrate fertilizer increased gross cubic volume growth
each year during the 7 years following treatment. As the dosage increased from 140
through 280 to 420 pounds of nitrogen per acre, (1) annual increment increased, (2)
peak annual growth occurred later and continued longer, and (3) duration of response
will probably be extended by several years.
-
Mortality Volume Was Increased by Heavy Dosages of N
Application of 280 or more pounds of nitrogen increased mortality losses in
total and merchantable volume (table 6). Following treatment with 280 r 420 pounds
I
N, there was a two- . and four-fold increase, respectively, in total mortality volume
(CVTS) during the 7-year period. Most losses occurred in nonmerchantable volume.
An average of less than 1 percent of mortality was merchantable volume on control
plots compared with 22 to 28 percent on fertilized plots.
Net Cubic-Volume Growth Was Greatest With 280 Pounds N
Although gross growth in CVTS and CV4 increased with increasing nitrogen
dosage, so did mortality. Consequently, net growth in both volume standards was
greatest with 280 pounds N.
�/ Personal communication with stanley P.
ton, in March
1972. Gessel, Professor, University of Washing­
Table 6.--Average volume of mortality, 1964 through 1970, per acre basis
CVTSY
Cubic
feet
I
Percent of
unfertilized
100
0
146
140
203
139
280
349
583
399
420
I
Percent of
gross growth
239
16
14
20
30
Cubic
feet
11 0
44
I
Percent of
. unferti1 ized
100
I
Percent of
gross change
0
m
96
3
00
148
5
m
7
II Pounds of nitrogen per acre. Y Cubic volume of total stem, trees 1.5-inch d.b.h. and larger, mortality volume based on adjusted gross and net CVTS.
11 Cubic volume to a 4.0-inch top d.i.b., trees 5.6-inch d.b.h. and larger.
11 Some mortality in CV4 did occur in O-N plots; however, the mathematical,
linear fit to treatment means removed this.
15
I
! ..
Net volwne growth of the total s tand
Depending on amount of applied
nitrogen, net CVTS growth on fertilized plots averaged 458 to 649 cubic feet per
acre or 58 to 83 percent more than that on control plots dtTing the 7-year period
(fig. 6 ) . The response surface was significantly curvilinear (p < 0. 03).
.--
Net change in merchantable volwne. --CV4 volume of the live stand increased
by an additional 336 to 1, 010 cubic feet per acre or 33 to 98 percent after fertilizing:
Net gain in CV4
Treatment
140 N
280 N
420 N
Cubic feet
336
673
1, 010
Percent
33
65
98
CONSIDERATIONS FOR THE LAND MANAGER
WHAT RATES OF NITROGEN SHOULD BE USED?
In this study area, magnitude and duration of response in gross cubic volume
were related positively to amount of ammonium nitrate applied. Response to the
140-N treatment appears nearly complete after seven growing seasons; however,
response to double and triple dosages have not yet ended, so we cannot yet accurately
compute fertilizer efficiency and thus optimum dosage.
Intensity of stand management or risk from winter breakage may be other bases
for deciding the appropriate nitrogen dosage for specific stands. One could use small
dosages in accessible, intensively managed stands and larger dosages in less access­
ible stands. In this study area, dosages of 280 and especially 420 pounds of N per
acre increased risk of winter breakage and mortality. In similar areas prone to
winter breakage, foresters may choose to adjust nitrogen dosage to increase or
decrease winter breakage and mortality; they may wish to increase this breakage
in overstocked stands and minimize it in understocked stands. To minimize winter
breakage, Nebe (1970) suggested restricting fertiliZing to stands having a uniform
crown canopy and regularly shaped crowns. Even when such stand conditions do
exist--as:i,n our plantation--silviculturists should avoid sudden stimulation of a heavy
foliage complement by heavy dosages of nitrogen.
Treatment cost, per pound of nitrogen applied, is likely to decline slightly, if
dosage per application is increased from 140 to 420 pounds N per acre. At dosages
of 150 and 200 pounds N per acre as urea prill, contractors will commonly supply
fertilizer and helicopters to fertilize large forested areas (approximately 1, 000
acres or more) for about $0. 11 per pound of N (Strand and Miller 1969). Increasing
dosage would increase construction and operational costs of each heliport; however,
these costs would be apportioned to a larger tonnage of fertilizer. The increase in
costs are likely to be proportionately less than the increase in dosage; therefore,
costs per pound of N applied from each heliport would decrease as dosage increased.
Assuming that increased dosage would not affect the acreage treated from each heli­
port, and thus the number of heliports needed, then costs of changing heliports would
16
be apportioned to a larger tonnage of fertilizer and further reductions in costs per
unit of N would result. More reduction is possible if increasing dosage encouraged
use of more efficient equipment or increased competition among bidders. i/
WHAT S OURCE OF NITROGEN SHOULD BE USED?
We do not lmow if comparable gains in volume growth would have been obtained
in this study had a nitrogen source other than ammonium nitrate been used. Most
nitrogen fertilizer currently applied to forests in the Pacific Northwest is urea,
primarily because its higher concentration (46-percent N) insures a greater net
payload than do other fertilizers such as ammonium nitrate (34-percent N). There
is concern, however, that urea applications during dry, warm weather can lead to
gaseous losses of N (Watkins et al. 1972) and reductions in the amount available for
growth. Currently, there is insufficient evidence from tests in Douglas-fir to specify
circumstances where the various nitrogen fertilizers will differ in response per
pound of nitrogen applied.
FERTILIZER CAN INCREASE USABLE YIELDS
Where natural productivity is restricted by nutrient defiCiencies, fertilizers
can increase usable yields per acre and enable the land manager to make earlier
commercial thinnings or final harvests. Fertilizer can increase the amount and
advance the timing of yields in several ways.
1. By supplying a growth-limiting factor and thus improving natural site
productivity. Field trials have demonstrated that insufficient available nitrogen
can limit maximum growth on Sites I through V (Strand and Miller 1969).
2. By stimulating growth of upper crown classes more than that of lower
classes. We found this in our diameter growth analysis.
3. By accelerating diameter growth of small trees and thus rate of ingrowth
into merchantable size classes. We found no strong evidence for this in our study.
4. By accelerating the natural rate of mortality of smaller trees in Douglas­
fir stands through suppression (Crossin et al. 1966 ).21 or through differential winter
breakage and mortality, as found in this study. Even on nutrient-deficient sites,
however, it is unlikely that the release provided by fertilizer- induced mortality
will be as ffective in stimulating growth of crop trees as that provided by mechanical
or chemical thinning methods.
Besides affecting volume growth, fertilizer can also affect wood quality. A
major concern is that increasing tree ring width lowers specific gravity of the wood.
Potentially, reduced specific gravity lowers structural strength and pulp yield per
unit volume (Larson 1968). In Douglas-fir, average specific gravity is generally
iI Personal correspondence with Robert
of Natural Resources, in June
§/ Unpublished data
1972.
Bergland, Forester, Washington Department
(Black Rock Fertilizer Study) on file at the Forestry Sciences
Laboratory, Olympia, Washington.
17
reduced after fertilization with nitrogen alone or in combination with other elements.
Maximum reductions of 8 percent (Erickson and Lambert 1958) and 10 percent
(Siddiqui et al. 1972) have been reported. Two recent studies in. Douglas-fir have
shown that fertilization improved fiber and paper quality despite substantial increases
in volume growth (Gladstone and Gray 1973). In assessing the effects of fertilization
on wood quality and quantity, the net effects of changes in wood quality must be offset
by the value of additional wood volume beyond that necessary to cover the cost of
fertilization. If pulp yields or pulp properties, or lumber grades and recoveries,
are not affected adversely by treatment, then volume increases due to fertilizer may
be accepted as a valid measure of gain from treatment (Gladstone and Gray 1973).
COMBINATION OF FERTILIZlNG AND THINNING
HOLDS PARTICULAR PROMISE
Some of the growth increases from fertilization will be in trees or portions of
trees which remain nonmerchantable. This is particularly true in young, natural
stands on low quality sites. To increase the usable gains from fertilizing, there is
a need to concentrate growth on fewer trees. The land manager can acc mplish this
by combining fertilizing and thinning.
Similarly, the benefits from thinning can be increased by combining this practice
with fertilizing. Thinning generally results in a temporary loss of full site occupancy;
however, foresters believe that this reduction in total growth per acre is usually
offset by the increased growth added to crop trees. One extreme case of growth
reduction following thinning occurred within 0.1 mile of our study area and in a por­
tion of the same plantation. For 6 years after the stand was thinned from 650 to 350
or fewer stems per acre, basal area growth per acre was roughly proportional to
growing stock; growth on the most lightly thinned plots averaged 63 percent of control
growth.&/ Based on our study results in the same plantation, we assume that appli­
cation of nitrogen fertilizer before or after thinning would have stimulated growth of
residual trees and increased per acre production.
In another study area on the Olympic National Forest, we fertilized previously
thinned portions of a Site IV stand of Douglas-fir. During the 2 years after fertilizing,
basal area.)growth of the thinned and fertilized stand was nearly equal to, and that of
the thinned-only stand only one-half, that of the unthinned stand.Y Thus, on nutrient­
deficient sites, fertilizer is a means for lessening temporary reductions in total
growth following thinning as well as for further increasing the growth added to re­
leased crop trees.
§/ D.
study.
L. Reukema.
1959.
Unpublished report on the Planting Creek increment spacing
Copy on file at the Forestry Sciences Laboratory, Olympia, Washington.
Jj Unpublished data (Rocky Brook
p.
Fertilizing-Thinning Study) on file at the Forestry
Sciences Laboratory, Olympia, Washington.
18
10
EFFECT OF NITROGEN FERTILIZATION ON WATER QUALITY i
f
1
The increasing use of nitrogen fertilizers in the Pacific Northwest to increase
forest growth has triggered concerns about the effects of this practice on environ­
mental quality, specifically a concern for excessive nitrogen in surface and ground
water. In response to this concern, stream waters flowing from numerous forested
watersheds in western Washington and Oregon have been analyzed before and after
applications of 150 to 200 pounds of N per acre as urea fertilizer. Such applications
have not resulted in toxic levels of urea-, ammonia-, nitrite-, or nitrate-nitrogen
in streams draining treated areas during the first year after treatment (Moore 1972).
Most research results indicate that direct application to surface waters is the princi­
pal means of entry of fertilizers and other chemicals to forest streams (Norris and
Moore 1972). Although additional information is needed about the effects of repeated
fertilization to the same area and other nitrogen carriers, such as ammonium nitrate,
available information suggests that little environmental damage appears possible if
fertilizer is carefully broadcast at current dosages and intervals on t e forested
'
lands (Tarrant et al. 1973).
ACKNOWLEDGMENT
The authors thank the following technical reviewers for their comments and
advice: Tomas Atzet, Lee Cromley, and Asa Twombley of U.S. Forest Service,
Region 6; Dennis Schweitzer of U.S. Forest Service, Intermountain Forest and
Range Experiment Station; Robert Tarrant and, particularly, Donald Reukema and
Floyd Johnson of U.S. Forest Service, Pacific Northwest Forest and Range Experi­
ment Station.
,
!
LITERATURE CITED
Crossin, E. C., J. A. Marlow, and G. L. Ainscough
1966. A progress report on forest nutrition studies on Vancouver Island
.;
For. Chron. 42(3): 265-284.
•
Erickson, Harvey D., and Gregory M. G. Lambert
1958. Effects of fertilization and thinning on chemical composition, growth,
and specific gravity of young Douglas-fir. For. Sci. 4(4): 307-315.
Gessel, S. P. , T. N. Stoate, and K. J. Turnbull
1969. The growth behavior of Douglas-fir with nitrogenous fertilizer in
western Washington. The second report. 119 p. , illus. Inst. For.
Prod., Univ. Wash. , Seattle.
Gladstone, William T., and Richard L. Gray
1973. Effects of forest fertilization on wood quality. In Forest fertilization
Symp. Proc., p. 167-173. USDA For. Servo Gen. Tech. Rep. NE-3.
Northeast. For. Exp. Stn., Upper Darby, Pa.
19
Handley, D. L., and L. V. Pienaar
1972. Forest nutrition studies in Douglas-fir on Vancouver Island: A second
report. For. Chron. 48(2): 88-91.
Heilman, Paul
1971. Effects of fertilization on Douglas-fir in southwestern Washington.
Wash. Agric. Exp. Stn., Circ. 535, 23 p.
Hoyer, Gerald E.
1966. Tarif access tables for the Pacific Northwest; a compilation. Wash.
State Dep. Nat. Resour., Olympia.
Kreutzer, K.
1967. Ern3.hrungszustand und Volumenzuwachs von Kiefernbestanden neuer
D Ungungsversuche in Bayern. Forstwiss. Centralbl. 86: 28-53.
Larson, Philip R.
1968. Assessing wood quality of fertilized coniferous trees. InForest
fertilization
theory and practice, p. 275-280. Tenn. Val. Auth.,
Muscle Shoals, Ala.
• • •
McArdle, Richard E., Walter H. Meyer, and Donald Bruce
1961. The yield of Douglas fir in the Pacific Northwest. U.S. Dep. Agric.
Tech. Bull. 201, 74 p., illus.
Moore, Duane G.
1972. Fertilization and water quality. In Annu. Meet. West. Reforestation
Coord. Comm. Proc. 1971: 28-31. Portland, Oreg.
Nebe, W.
1970.
Fertilizer trials in older pole-stage stands of Norway spruce (Uber
Dungungsversuche in alteren Fichtenstangenholzern.) Arch. Forstw.
19: 1037-1048.
Norris, Logan A., and Duane G. Moore
1972. The entry, fate and toxicity of forest chemicals in streams. In
Forestry and water quality, p. 45-67. Oreg. State Univ., Corvallis.
Pacific Northwest River Basins Commission Meteorology Committee
1969. Climatological handbook, Columbia basin states, precipitation. Vol. 2,
262 p. plus appendices. Vancouver, Wash.
Pesek, John, George Stanford, and N. L. Case
1971. Nitrogen production and use. In Fertilizer technology and use, 2d ed.,
p. 217-269. Soil Sci. Soc. Am., Inc., Madison, Wis.
20
Reukema, Donald L.
1968. Growth response of 35-year-old, Site V Douglas-fir to nitrogen fertilizer.
USDA For. Servo Res. Note PNW-86, 9 p., illus. Pac. Northwest For.
& Range Exp. Stn., Portland, Oreg.
I
-
Siddiqui, K. M., W. T. Gladstone, and Renata Marton
1972. Influence of fertilization on wood and pulp properties of Douglas-fir.
Proceedings of the Symposium on the effect of growth acceleration on
the properties of wood, C-1 - C-18.
Staebler, George R.
1955. Gross yield and mortality tables for fully stocked stands of Douglas-fir.
USDA For. Servo Pac. Northwest For. & Range Exp. Stn. Res. Pap.
No. 14, 20 p., illus. Portland, Oreg.
Stevenson, I. L.
1964. Biochemistry of soil. In Chemistry of the soil, 2d ed.,
Am. Chem. Soc. Monogr. No. 160.
pi
242-291.
Strand, Robert F., and Richard E. Miller
1969. Douglas-fir growth can be increased report from Pacific Northwest
shows. For. Ind. 96(11): 29-31.
Tarrant, R. F., H. J. Gratkowski, and W. E. Waters
1973. The future role of chemicals in forestry. USDA For. Servo Gen. Tech.
Rep. PNW-6, 10 p. Pac. Northwest For. & Range Exp. Stn., Portland,
Oreg.
i!
Tarrant, Robert F., and Richard E. Miller
1963. ,Accumulation of organic matter and soil nitrogen beneath a plantation
of red alder and Douglas-fir. Soil Sci. Soc. Am. Proc. 27: 231-234.
Turnbull, K. H., Gene Roy Little, and Gerald E. Hoyer
1963. Comprehensive tree-volume tarif tables. Wash. State Dep. Nat.
Resour., Olympia.
!
t
I
J.
Watkins, S. H., R. F. Strand, D. S. DeBell, and J. Esch, Jr.
1972. Factors influencing ammonia losses from urea applied to northwestern
forest soils. Soil Sci. Soc. Am. Proc. 36: 354-357.
Wise, William S.
1970. Cenozoic volcanism in the Cascade Mountains of southern Washington.
Wash. State Dep. Nat. Resour. Bull. No. 60, 45 p.
21
APPENDIX
PRETREATMENT CONDITIONS
Stand. --Planted in spring 1929 with 1-1 Douglas-fir from an offsite, Roy,
Washington, seed source,.§/ the stand was 37 years old when fertilized in April 1964.
Spacing in the original planting averaged 8 by 8 feet or about 680 trees per acre.
Prior to fertilizing, plots averaged 604 live trees per acre and 94. 5 square feet of
basal area (table 7). Site index averaged 82 and ranged from 75 to 90 feet (height at
age 100). Basal area per acre in all of these plots was below normal standards
(McArdle et al. 1961). Expressed as a percent of normal for the indicated site index
for each plot, stocking among plots before 1964 growing season ranged from 65 to
98 percent of full stocking, averaging 80 percent.
'§/ Written correspondence with Tom Atzet,
Forest, on February
.1
23, 1973
District Forester, Gifford P inchot National
•
Table 7.--Stand conditions prior to fertilizing, total stand, per acre basis
Treatment.!.!
and
plotY
0:
140:
Site
index
(feet)
Basa 1 area
(sq. ft.)
Basa1 area,
percent normalll
7
1
5
540
580
680
79
75
81
81.9
91.9
113.5
73
90
98
Mean
600
78
95.8
88
3
9
8
480
600
640
75
'85
82
71.4
91.9
106.1
70
74
90
Mean
573
81
89.8
77
580
720
580
90
77
88
86.4
95.4
112.8
Mean
627
85
65
89
87
98.2
79
6
4
10
540
620
700
84
81
88
84.8
89.1
109.2
70
77
85
Mean
620
84
94.4
77
604
82
94.5
80
280:
2
,;)12 11
420:
Number
of live trees
All treatments:
Mean
.!.! Pounds of nitrogen per acre.
Y Plots are arranged within treatment in ascending order of initial
cubic volume.
1I Richard E. McArdle, Walter H. Meyer, and Donald Bruce. The yield
of Douglas fir in the Pacific Northwest. U.S. Dep. Agric. Tech. Bull. 201,
74 p., illus., 1961.
22
+
Location. --The study area is located 3 . 5 miles northwest of the Wind River
Ranger Station near Carson, Washington, at an elevation of approximately 2, 000 feet.
Topography is relatively uniform, with northwest aspect and slopes ranging from 15
to 30 percent. The plantation lies on the east edge of the 294, ODD-acre Yacolt Burn
in an area that was swept by wildfires in 19 02 and 1927 .
I
Climate . -- Based on weather records ( 1956 through 1965) from the Wind River
Ranger Station, 9 0 0 feet lower in elevation than the study area, annual precipitation
averages 96 inches with 26 percent falling during the April through October period
(Pacific Northwest River Basins Commission Meteorology Committee 1969). Poten­
tial evaporation during the summer months greatly exceeds summer precipitation,
so trees in the study area are subjected to summer moisture stress characteristic
of western Washington and Oregon.
Most precipitation falls between growing seasons as rain, snow, or a mixture.
Winter temperature is normally near or above freezing; thus ice accretion as glaze
or rime is likely to occur .
. SoiZs. -- The soil in the study area is moderately deep and well-drained; it
is derived from andesitic or rhyodacitic pyroclastic rocks of the Ohanapecosh Forma­
tion from early Tertiary times (Wise 1970).
Surface horizons contain some pumice
and basaltic gravel from recent Pleistocene time. This soil (Number 87) has been
mapped on nearly 10, 000 acres of the Gifford Pinchot National Forest. g,1 Morpho­
logically related soils cover an additional 23, 0 0 0 acres of the Forest.
Surface soil on the study plots has fine gravelly loam texture and granular
structure ; below the 6- to 17-inch depth, the soil has a clay-loam texture and strong,
subangular blocky structure . Roots are abundant in the surface layer, but sparse
below 3 feet. The soil contains approximately 3, 000 pounds of total nitrogen per
acre to a 3-foot depth (Tarrant and Miller 1963). This amount is about average for
low productivity lands in western Washington; probably less than 5 percent of this
total is available for vegetative use each year (Stevenson 1964, Pesek et al. 19 7 1) .
EXPERIMENTAL DESIGN AND TREATMENT
\
In A'pril 1964, ammonium nitrate (33. 5-percent N) was applied to O. 15- acre
circular plots at rates of 140, 280 , and 420 pounds of N per acre. 10 / Each treat­
ment was replicated on three plots. Three control plots were also included in this
completely randomized experimental design.
J
:
Y Written correspondence with LeRoy Meyers,
Region
6,
on December
10/ Rates
and
600
28, 1971.
Soil Scientist, U. S. Forest Service
of nitrogen application were previously reported (Reukema
pounds of nitrogen per acre.
actually treated and thus rates were
1968)
as
200, 400,
Subsequently, we found that a larger plot area had been
140, 280,
and
420
pounds.
23
MEASUREMENTS AND VOLUME
DETERMINATION
Trees were measured on a O. 05-acre circular plot centered within the treated
plot. Trees were initially measured after the 1963 growing season, subsequently
measured after two growing seasons, and then measured annually through 19 70. At
each measurement, d. b . h . was measured on all trees and total height determined
on a subsample of seven to 15 trees per plot distributed over the range of
diameters, 1 1/ but with two-thirds of the subsample larger than average d. b. h.
Local volume tables for plot volume estimation were derived by means of the
tarif system (Turnbull et al. 1963). Tarif numbers 12/ were obtained from Hoyer
(1966). For each treatment level, an average tarif number was computed based on
more than 30 trees which had been measured for total height in 1963, 1967, and
1970. Average tarif numbers for intervening years were obtained by graphic inter­
polation. The average tarif number of each treatment level was used to calculate
plot volumes at each inventory. Initially, the average tarif numbers a¢ong treat­
ment levels ranged between 24. 3 and 25. 5 . By the end of the seventh growing season
after treatment, the range had widened to between 26. 8 and 28. 9, with larger in­
creases associated with the higher fertilizer levels
•
..)
11/
Initially, height was measured on seven trees per plot.
season, the height sample was increased to
15
1967 growing
1963 height of the
After the
trees per plot and the
supplemental trees was measured when possible.
12/Tarif-volume
equations provide a series of harmonized volume/d. b. h. curves, each
indexed by a tarif number.
for a tree of
1. 0
The tarif number is the cubic volume (from stump to a 4-inch top)
square foot of basal area.
24
G P O 9 9 4 - 1 84
l
The
AND
m i ss i o n
RANGE
k nowledge,
of t h e PAC I F I C N O R T H W E ST
E X P E R I M E N T STAT I O N
tech n o l o g y ,
and
a l ternatives
F O R EST
i s to provide t h e
for
prese n t a n d
f u t u re p ro tec t i o n , manage m e n t , a n d u se o f forest, r a n ge , a n d
r e l a ted e n v i r o n me nt s .
W ithin
this
overall
m i ss i o n ,
the Stat i o n c o n d u c ts a n d
s t i m u l a t e s research to f a c i l i t a t e a n d to accelerate progress
toward the f o l l o wi n g goa l s :
r o v i d i n g safe a n d e f f i c i e n t tec h n o logy f o r i nv e n t o r y ,
1. P
p r o te c t i o n , a n d u se o f reso u rces.
2 . D ev e l o p m e n t and eva l u at i o n o f a l te r n a t i v e methods
a n d levels o f resou rce management.
3. A c h ieveme n t o f o p t i mu m su sta i n ed resou rce p r o d u c­
t i v i ty consistent w i t h m a i n ta i n i ng a h i gh q u a l i ty f o r est
e n v i r o n me n t .
T h e a rea of research e n c o m passes O rego n , Wash i n gt o n ,
A laska, a n d , i n some cases, C a l i f o r n i a , H a wa i i , t h e Western
and t h e N a t i o n . R es u l ts of the research w i l l be made
a v a i l a b l e p r o m pt l y . Project h ea d q u a r ters a re a t :
Fairbanks, Alaska
Portland, O re g o n
J u n ea u , A l aska
O l y mp ia , Wash i n g t o n
O regon
S e a t t l e , Wash i ng t o n
Corva l l i s , O re g o n
We natchee, W a s h i n g t o n
L a G ra nde, O regon
Mailing address:
Pacific North west Forest and Range
Experim en t Station
P. O. Box 3 14 1
Portland, Oregon 91208
I
D e partme nt of A g r i c u l t u r e i s d e d icated
T h e F O R E ST S E R V I C E of the
t o the p r i n c i p l e of m u ltiple use m a n ag e m e n t of the N a t i o n 's forest resou rces
for s u s t a i ned y i e l d s of wood , wate r " forage, wild l i f e , and recreat i o n .
T h r o u g h f o r e s t ry research, coope r a t ion w i t h t h e States and p r ivate forest
N at i on a l G ra s s l a n d s , i t
o w n e r s , and m a n ag e m e nt of the N at i on a l F o rests
provide i n creasin g. l y greater service to
strives
a s d i r e cted 'by Congress --,
a grow i n g N a t ion .
T h e U . S . D e p a r t m e n t o f Agriculture is an E q u a l Oppo r t u n i t y E m p l o y e r .
A p p l i c a n t s for a l l D e partment programs wi l l
e q u a l co n s i d e r a t i o n
w i t h o u t r e g a r d to r a c e , color, seX or national